Billy Conn was born on October 8, 1917 in Pittsburgh, Pennsylvania. Conn never fought as an amateur. He was managed by Johnny Ray who fought as a lightweight and trained with hall of famer Harry Greb. Conn made his pro debut at age 16 when he lost a decision to 21 year old Dick Woodward. Most of Conn's early fights were against older, more experienced opponents. Conn began his career at welterweight and fought up to heavyweight. By the age of 21 Conn had defeated 9 present or former world champions. Almost one third of his fights were against title holders. Although often outweighed, Conn never lost to a heavyweight with the exception of Joe Louis.

Conn gained national attention with his upset victories over middleweight champion Fred Apostoli. At the time Apostoli was regarded as the best pound for pound fighter in the world. Conn beat him in his New York debut at Madison Square Garden with a 10 round decision and won again in 15 rounds just five weeks later. They were two of the most thrilling fights in middleweight history. Conn considered his fights with Apostoli the toughest of his career. Conn won the world light heavyweight title from Melio Bettina on July 13, 1939. He later gave up the title to campaign as a heavyweight.

Conn will forever be remembered for his near-upset of heavyweight champion Joe Louis on June 18, 1941 at the Polo Grounds in New York. Conn weighed in at 169 1/2 lbs and was outweighed by 30 pounds. Louis had beaten every top heavyweight and was in the prime of his career. Conn out-boxed and out-slugged Louis for 12 rounds and almost sent Louis to the floor at the end of the 12th. Overconfident and ahead on points going into the 13th round, Conn told his manager that he was going to knockout Louis. Ray told him that he was winning the fight and to keep boxing but Conn was determined to win by knockout. Conn came out slugging and was winning the first half of the round, but he was fighting carelessly. The bigger and stronger Louis eventually hurt Conn and after a number of unanswered blows he knocked out Conn with two seconds left in the round. Joe Louis said this fight was the toughest of his career and that Conn was the best light heavyweight he ever saw. This fight is often referred to as the greatest fight of all time.

Conn beat Hall of Famer Tony Zale in 1942 and had a rematch scheduled with Joe Louis the same year. However the rematch was canceled when Billy broke his hand in a much publicized fight with his father in law, major league ballplayer "Greenfield" Jimmy Smith. The two later apologized but Billy was sent on a moral tour with Bob Hope and others celebrities during World War II. When the war ended there was a rematch in 1946, but this time it was an older, slower Conn who hadn't had a professional fight in four years. Louis knocked out Conn in the eight round and Conn announced his retirement after the fight. Conn made a brief two fight comeback in 1948 winning both bouts, but then decided to retire for good.

Billy Conn possessed great hand and foot speed, had an excellent defense, boxed beautifully, and had an iron chin. He was a slow starter who never tired, fought best in the later rounds, and had a tendency to slug it out when hurt. He was generally regarded as the worlds most handsome fighter and starred in a movie for Republic Pictures called "The Pittsburgh Kid" in 1941. But he turned down a career in Hollywood, including a role in "On the Waterfront" to live in Pittsburgh with his wife Mary Louise.

At the age of 72 Billy Conn once again made national headlines by interrupting a convenient store robber in Pittsburgh. Billy decked the gunman who was later arrested. Billy Conn died in 1993 at the age of 75.